Journal
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 19, Issue 22, Pages 14533-14542Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7cp02004j
Keywords
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Funding
- National Science Foundation of China (NSFC) [21373259, 21301107, 11405256]
- Excellent Young Scientists Fund from the NSFC [21622106]
- Hundred Talents project of the Chinese Academy of Sciences
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA09030102]
- Taishan Scholar project of Shandong Province (China)
- Open Funding from Beijing National Laboratory for Molecular Science
- Open Funding from Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences
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A low-concentration cobalt (similar to 6 at%) and manganese (similar to 3 at%) bimetallic oxide catalyst supported on ceria nanorods (CoMnOx/CeO2), as well as its related single metal oxide counterparts (CoOx/CeO2 and MnOx/CeO2) was synthesized via a deposition-precipitation approach. The fresh samples after air-calcination at 400 C-omicron were tested under the reaction conditions of CO oxidation, and showed the following order of reactivity: CoMnOx/CeO2 > CoOx/CeO2 > MnOx/CeO2. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data identified that the structure of the CeO2 support was maintained during deposition of metal (Co, Mn) ions while the corresponding vis-Raman spectra verified that more oxygen vacancies were created after deposition-precipitation than those in pure ceria nanorods. Aberration-corrected, high-angle, annular dark-field scanning transmission electron microscopy (HAADF-STEM) images with the help of electron energy loss spectroscopy (EELS) analyses determined two types of cobalt species, i.e. ultra-fine clusters (< 2 nm) and smaller nanocrystals (up to 5 nm) in CoOx/CeO2 while only bigger nanostructures (similar to 10 nm) of cobalt-manganese oxides in CoMnOx/CeO2. X-ray absorption fine structure (XAFS) measurements demonstrated the presence of a cubic Co3O4 phase in all the cobalt-based catalysts. The fitting results of the extended X-ray absorption fine structure (EXAFS) indicated that the introduction of the secondary metal (Mn) oxide significantly enhanced the two-dimensional growth of cobalt oxide nanostructures on the surface of CeO2. Therefore, the enhanced activity of CO oxidation reaction over the bimetallic cobalt-manganese oxide nanocatalyst can be attributed to the higher crystallinity of the Co3O4 phase in this work.
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